1. Field of the Disclosure
This disclosure relates to synthesis of metal chalcogenide nanocrystals. Particularly, this disclosure relates to methods of synthesizing metal chalcogenide nanocrystals using organodichalcogenide reagents in which the size and shape of the nanocrystals is controlled.
2. Description of the Related Art
Nanotechnology has the potential to revolutionize medicine, electronics, and energy conversion; however, the development of valuable nanoscale materials is hampered by energy intensive synthetic methods that require high temperatures (>300° C.) and environmentally harmful chemicals. It is currently understood that the unique electrical and optical properties that nanocrystals have are a direct result of their size and shape. For example, elongated structures like nanorods and nanowires conduct electrical currents more efficiently compared to more symmetrical shapes like nanospheres. In order for nanotechnology to reach its full potential, it is therefore necessary to develop synthetic strategies that provide strict control over the final nanocrystals shape/size while operating at lower synthetic temperatures and use less toxic chemicals. The present synthetic method of solution-phase synthesis of metal chalcogenide nanocrystals using organodichalcogenide reagents provides an answer to these problems of synthetic difficulty.
Metal chalcogenide nanocrystals are one family of semiconductors that are potentially useful for biological imaging, flat-screen/touch-screen panels, chemical sensors, photovoltaics, thermoelectrics, etc. Currently, in order to incorporate the chalcogen (oxygen, O; sulfur, S; selenium, Se; tellurium, Te) energy-intensive synthetic techniques must be used such as vacuum deposition or laser ablation. Some solution-phase techniques, whereby the chemical precursors are mixed in solution to make the nanocrystal product, are more feasible for industrial scalability, but require high temperatures (>300° C.) for them to operate successfully.
Conventionally, organophosphine chalcogenides are employed as the chalcogenide source; however, because of the relative stability of the phosphorous-chalcogen bond, high temperatures are required for chalcogen transfer (Bawendi et al. J. Am. Chem. Soc. 2006, 128, 13032; Alivisatos et al. J. Am. Chem. Soc. 2007, 129, 305). Pettenkofer et al. Thin Solid Films 2005, 480, 347 discloses the use of a organodichalcogenide (di-tert-butyl disulfide) to make a metal chalcogenide (copper indium sulfide, CuInS2), but high vacuum techniques and molecular beams operating up to 1200° C. were used to create large (greater than nanoscale) CuInS2 films that contained impurities such as Cu2S and Cu2In. Elemental chalcogenides, another common source of S, Se, or Te, also require high temperatures for metal chalcogenide nanocrystal formation because of kinetic issues of dissolution. In addition, it currently remains difficult to control the ultimate shape and size of the final metal chalcogenides nanocrystals. These current drawbacks cause the synthesis of metal chalcogenide nanocrystals to be an expensive procedure that would ultimately increase the cost for the consumer in mass-produced technologies.